L-Carnitine is made in the body from the amino acids lysine and methionine. It increases the use of fat as an energy source by transporting fatty acids into the mitochondria, where they are "burned" to release energy for body functions. The L-carnitine form may cause adverse side effects however. It is available in several different forms including propionyl-L-carnitine and acetyl-L-carnitine. Propionyl-L-carnitine, through its enhancement of metabolism has been proven to prevent ischemia-induced heart dysfunction, and acetyl-L-carnitine has been suggested to delay the progression of Alzheimer’s disease. L-carnitine is found naturally in avocados, breast milk, dairy products, red meats (namely lamb and beef), and tempeh (fermented soybean product). A deficiency of L-Carnitine can cause muscle fatigue, cramps, or low blood-sugar levels.